Triple ball motor spindle drive

ABSTRACT

THE INVENTION RELATES TO A BALL MOTOR IN WHICH THERE ARE A NUMBER OF ROWS OF BALLS CONTAINED IN CYLINDERS, THE CYLINDERS AND BALLS IN ADJACENT ROWS BEING OF DIFFERENT SIZES. MEANS ARE PROVIDED TO RENDER INOPERATIVE ROWS OF CYLINDERS IN A PREDETERMINED ORDER SO AS TO PRODUCE A DESIRED TORQUE CURVE.

Uite tates Paten Inventors Donald Firth;

Sinclair Upton Cunningham, East Kilbride, Glasgow, Scotland Appl. No.782,664

Filed Dec. 10, 1968 Patented June 28, 1971 Priority Dec. 29, 1967 GreatBritain sa on 9 Assignee National Research Development Corporation,22990 En TRIPLE BALL MOTOR SPINDLE DRIVE 9 Claims, 8 Drawing Figs.

US. Cl 91/492, 91/180, 91/498, 92/72 Int. Cl F011b 1/06, FOlb 13/06Field of Search 103/161 (A) (Cursory); 91/180, 204, (inquired), 205,(Cursory), 492; 60/53 (B) (Cursory); 92/72 [56] References Cited UNlTEDSTATES PATENTS 1,488,528 4/1924 Cordini 2,160,612 5/1939 Alpern.2,163,080 6/1939 Benedek..... 2,303,685 12/1942 Eden et al.., 3,199,2978/1965 Croswhite Primary Examiner- Paul E Maslousky Attorney-Cushman,Darby and Cushman ABSTRACT: The invention relates to a ball motor inwhich there are a number of rows of balls contained in cylinders, thecylinders and balls in adjacent rows being of different sizes. Means areprovided to render inoperative rows of cylinders in a predeterminedorder so as to produce a desired torque curve.

PATENTED JUN28 sen SHEET 1 BF 5 n\ \w kwll PATENTEB JUN28 I971 SHEET '4OF 5 PATENTEU IJUN28 1971 SHEET 5 BF 5 K u Q r TRIPLE BALL MOTOR SPINDLEDRIVE This invention relates to multicylinder piston motors. An objectof the invention is to provide a multicylinder piston motor in which thetorque capacity of the motor can be arranged to follow a predeterminedcurve.

According to the invention such a motor comprises a number of operatingcylinders of different capacities and means to render one or morecylinders inoperative whereby the torque of the motor may be made tofollow a predeter' mined curve.

The invention has particular, but not exclusive, application tomulticylinder piston motors in which the pistons are in the form ofballs. Ball motors are well known in themselves and usually comprise aplurality of rows of balls (of the same size) acting on a track or camsurface to produce relative rotation- -see for example copending BritishPat. application Nos. 33412/64 and 56784/66. Such motors may be rotaryor linear.

According to one aspect of the invention there is a ball motor with aplurality of rows of balls in cylinders the balls in each row being ofadifferent size to the balls in the other rows, means to supply operativefluid to all the ball containing cylinders and means to renderinoperative one or more rows of cylinders.

Preferably, operating fluid for all the rows of cylinders and pistons issupplied through a common valve. Preferably, the means to renderinoperative one or more rows is in the form of an isolating valvelocated between adjacent rows of cylinders. Preferably, there are atleast three rows of cylinders with isolating valves located between eachadjacent pair of cylinders. Preferably, the isolating valves arecircular valve plates with apertures in them adapted to register withports in the body of the motor containing the rows of cylinders.

According to another aspect of the invention in a ball motor of the kindin which a'number of balls bear against a cam track, the balls beingcontained in cylinders, and there being a number of rows of thecylinders, the sizes of the balls in the different rows are so chosenthat by rendering inoperative rows of balls in sequence a predeterminedtorque curve is produced.

The number of rows of balls and the number of balls per row is dependenton the desired horsepower and torque curve of the motor, three rows ofballs being shown in the following example merely as one possibleconfiguration.

When a row of cylinders is rendered inoperative by cutting off thesupply of operating fluid to it, it is necessary to provide means todrain the inoperative cylinders to prevent blockage.

This may be done by the same valves which are used to render the row ofcylinders and pistons inoperative. The valve can include one or moreapertures arranged, in the closed position of the valve, to connect thecylinders to a drain channel or channels so as to exhaust any fluidcontained in the cylinders.

In the accompanying drawings is shown a ball motor, having three rows ofballs of different sizes, embodying the invention.

In the drawings:

FIG. 1 is a longitudinal section through the ball motor;

FIG. 2 is a section on the line AA shown in FIG. 1;

FIG. 3 is a section on the line BB shown in FIG. I;

FIGS. 4 and 5 are scrap sections on the line CC showing the valverespectively in its closed and opened positions, the line CC being shownin FIG. 6;

FIG. 6 is a scrap section of part of the motor embodying one of thelarger balls;

FIG. 7 is a graph showing a comparison between a constant horsepowertorque curve and the torque plotted against r.p.m. for a motor notembodying the present invention and having three rows of balls ofidentical size so that the three rows have the same capacity; and

FIG. 8 is a similar curve showing how the torque available from asimilar motor incorporating the present invention i.e., with differentsizes of balls in the rows of cylinders, approaches much more closelythe desired falling torque curve.

The motor shown in FIG. 1 comprises a cylindrical casing 10 within whichis mounted a cylinder block 11 containing three rows of cylinders 12, 13and .14, containing balls 12a, 13a and 14a respectively, the diameter ofthe cylinders 12 being less than the diameter of cylinders 13 which isin turn less than the diameter of cylinders 14. There are eightcylinders in each row. A spindle 15 is supported in the casing 10 byhydrodynamic bearings 16a and 16b. Attached to spindle I5 is aneccentric cam track 12b for the cylinders 12, a track 13b for thecylinders 13, and a track 1412 for the cylinders 14.

The track 14b can be seen more clearly in FIG. 2 from which it will benoted that this is a conventional ball motor in which fluid is suppliedto the cylinders 14 in such a way that the balls I4e bear against theeccentric track 1412 so as to drive the spindle 15. The principleinvolved is well known and will not be described in detail.

Oil is supplied to the balls through a primary fluid flow or oil inletpassage 17 and there is a primary fluid return passage 18. The oil inletpassage 17 leads to a drilling 19 in the spindle 15 the drilling 19being blocked at its outer end by a plug 20. The oil passes along thedrilling 19 to a pintle valve 21. The valve 21 rotates with the spindle15 and has a number of arcuate slots such as 22 round its exterior whichwill successively feed the eight passages 23, each of the passages 23leading to one of the cylinders 12 via a secondary fluid supply andexhaust connecting passage 24. The pintle valve 21 is also connected toan oil return drilling 25 in turn connected through an annular groove 26to the oil return passage 18.

Oil supplied and exhausted through the eight passages 24, will, as shownin FIG. I, reach all three rows of cylinders, but between row 12 and row13 is a valve plate marked V2 and between row 13 and row 14 is anothervalve plate marked V1. These valve plates have apertures which, in theposition shown in FIG. 1, allow the flow ofoil to all three rowsofcylinders. As shown in FIG. 3 each valve plate can be rotated to aclosed position in which it blocks all the passages 24. The rotation ofthe valve plate is achieved by an arm 25 connected to the valve plate V1and movable through an arc of 15 by an electromagnetically operatedpiston device 26. There will be a similar operating arm for the valveV2.

Considering for the moment the valve V1, between rows of cylinders 13and 14, it will be seen that the supply and exhaust offluid to the rowsof cylinders 14 can be cut off and the cylinders 14 isolated by movementof the valve plate V1. When this is done, the balls free wheel" and donot take part in driving the motor. The oil which would then be trappedbetween the balls 14a and the outer ends of the cylinders 14 is allowedto leak as illustrated in FIGS. 4, 5, and 6. FIG. 5 shows the valve VIin the open position in which a milled slot 27 in the face of the valveplate does not connect the cylinder 14 to a drilled hole 28 in thecylinder block. In the position shown in FIG. 4 where the valve isclosed, exhaust oil from each of the cylinders 14 of the idle ball motorpasses through the respective milled slot 27 and drilled hole 28 to acommon annular drain channel 31 around the spindle IS. The drain channel31 communicates with the ends of the cylinders remote from the passages24, and also with the casing 10 as seen to the right of cylinder 14 inFIG. I.

The valve plate V2 is similarly provided with milled slots connecting toanother drilling, not shown, and thence to channel 31.

When both valves V1 and V2 are closed both cylinders 13 and 14 areisolated from the oil supply and return passages, and only cylinders 12and balls 12a are effective to drive the spindle 15.

In FIG. 7 is shown a falling torque curve 29 corresponding to constanthorsepower. If three rows of cylinders of identical capacity were usedby cutting out first one row and then a second row, the torque availablewould be as shown in the dotted line 30 in FIG. 7.

By using the present invention the torque is as shown in the dotted linein FIG. 8 which will be seen to be much closer to the desired torquecurve.

In selecting the sizes for the various rows and the speed range overwhich each motor operates, the following desiderata apply:

1. The pump flow (of the pump which supplies the driving fluid) shall bethe same at the maximum speed in each range. This ensures bestutilization ofthe pump.

. The pressure at the beginning of each speed range will be equal to themaximum design pressure for the motor. This makes certain that the motorsize for each of the speed ranges will be a minimum. These conditions,together with the equations relating to torque. pressure, speed andpower, allow the motor sizes and the speed ranges to be calculated.

It is wasteful to have more capacity than is required because thisresults in a higher oil flow at a low pressure. In the example given,the torque capacity (or displacement) of the equal stage motor is sixtimes the flow required for the graded ball motor at a maximum speed andthe pressure is six times lower for the same power.

In general, the more stages in a motor then the more closely the torquecapacity curve can follow the constant horsepower requirement. It willbe appreciated that there is no limit to the number of stages that canbe designeduntil the motor becomes unacceptably long. The choice of balland lobe numbers depends on the torque speed requirements.

In the illustrated arrangement we require only one pintle or distributorvalve'and this is designed to operate on a small diameter so thatfriction losses are small. The same number of balls and cam lobes areused in each row so that only one pin tle is necessary.

It will be apparent to those skilled in the art that while the inventiondescribed herein was described in the context of its use as a motor,ball motors of this type may as well be operated as pumps. This may beaccomplished by merely driving the motor shaft, in this case spindle l5.As is common in the art, the generic term machine" may be used to referto either a motor or a pump usage.

We claim:

l. A multicylinder piston machine comprising:

a primary fluid flow passage and a primary fluid return passage;

two rows of piston-and-cylinder assemblies, each row having a respectivecam track with the same number of lobes to relate reciprocatory motionof the associated assemblies on the one hand, with motion peripherallyof said cam track on the other hand;

a plurality of secondary fluid supply and exhaust passages eachcommunicating with a respective pair of corresponding ones of saidassemblies, one from each of said rows;

a pintle valve for permitting communication of both of said primarypassages with said secondary passages in predetermined successivemanner, said primary passages being communicated in alternating sequencewith each one ofsaid secondary passages; and

an isolating valve including a common valve member disposed intermediatesaid two rows and operable to open and close secondary passages leadingto one of said rows in unison to respectively communicate and isolatesaid one of said rows relative to said primary passages.

2. A machine according to claim 1 comprising:

a fluid drain channel, and wherein said isolating valve is furtheroperable to respectively isolate and communicate said drain channelrelative to said one row.

3. A machine according to claim 2 wherein said drain channelcommunicates with the ends of the cylinders of said one row ofassemblies remote from said secondary passages.

4. A machine according to claim 1 wherein the piston of each of saidassemblies is in the form ofa ball.

5. A machine according to claim 1 wherein said rows of assemblies haverespectively different capacities.

6. A machine according to claim 1 wherein said rows are of each ofcircular form axially spaced one from the other along a common axis,with said secondary passages disposed in the form ofa cylindrical arrayabout said axis.

7. A machine according to claim 5 comprising:

a fluid drain channel, and wherein said common valve member is disposedfor rotation about said axis to intersect said secondary passages;

said member having a plurality of apertures therethrough to respectivelyopen said secondary passages in one rotational position of said member;and

having a plurality of grooves in the face of said member nearer said onerow to communicate the same with said drain channel in anotherrotational position of said member.

8. A machine according to claim 7 wherein said member is in the form ofan annular plate provided with a plurality of radial bores communicatingrespective ones of said grooves with said drain channel.

9. A machine according to claim 1 comprising:

a third row of piston-and-cylinder assemblies similar to said two rowsand communicated with said primary passages by said secondary passages;and

a second isolating valve including a second common valve member disposedintermediate said third row and said two rows, and operable to open andclose said secondary passages in unison to respectively communicate atleast one of said two rows, dependent on the operable position of thefirst-mentioned common valve member, and isolate said two rows relativeto said primary passages.

